lib1512.c: Fixed compilation warning

An enumerated type is mixed with another type.

...as well as a small coding style error.

tests/libtest/lib1512.c

@@ -34,7 +34,7 @@
 
 int test(char *URL)
 {
-  CURLcode res = 0;
+  int res = 0;
   CURL *curl[NUM_HANDLES] = {NULL, NULL};
   char *port = libtest_arg3;
   char *address = libtest_arg2;
@@ -84,6 +84,6 @@ test_cleanup:
   curl_slist_free_all(slist);
   curl_global_cleanup();
 
-  return (int)res;
+  return res;
 }